KETO ACIDS FORMED BY BAKER'S YEAST

Abstract

The keto acids formed in baker's yeast during anaerobic fermentation and aerobic growth were identified, by means of thin-layer chromatography, as their 2,4-dinitrophenylhydrazones and as corresponding amino acids after reduction of the hydrazones. Pyruvic acid, α-ketoglutaric acid and p-hydroxyphenylpyruvic acid, were found in abundance. In addition, the following keto acids were present in estimated descending order of magnitude: α-keto-β-methylvaleric acid, α-keto-isovaleric acid, α-keto-isocaproic acid and β-phenylpyruvic acid, and small amounts of α-ketobutyric acid, oxalacetic acid and α-keto-γ-methiolbutyric acid. Under anaerobic conditions a somewhat larger amount of keto acids accumulated in the medium than under aerobic conditions, but in both cases the amounts rose markedly as the content of seed yeast increased.